Limitation in the number of parts is now a requirement in footwear manufacturing to meet shortage of materials. Further, in order to manufacture a footwear bottom, it is necessary to use a large number of parts and hence to perform many fitting-up and assembling steps, which results in waste and other disadvantages.
Attempts have been made to remove these and other disadvantages by utilizing the physical and technological properties of molding resins. However, special manufacturing methods are necessary in processing these components since the use of these materials does not meet the wearer's requirements fully and rationally. In particular, a shoe structure must simultaneously meet the requirements of flexibility, rigidity, wear resistance, transpiration and impermeableness. Accordingly, if one part of a shoe, for example the plantar support, meets some of these requirements, it obviously does not fulfil the other requirements; typical of this is flexibility on the one hand with pressure or load resistance on the other.